1. Field of the Invention
The present invention relates to polyvinyl chloride (hereinafter "PVC") pallets or crates used for support and transport of goods. Specifically, the present invention relates to PVC pallets or crates built from PVC profiles and a bonding agent, and a method of making PVC pallets or crates.
2. Description of the Prior Art
Plastic pallets have been used in warehouses for supporting various goods, such as beverages. The pallets are typically transported within the warehouse with a fork-lift truck, or a pallet-jack. Examples of prior plastic pallets can be found in U.S. Pat. Nos. 5,492,069 to Alexander et al.; 5,456,189 to Belle Isle; 5,042,397 to Fielder; 3,966,529 to Kuroda; 3,938,448 to Nishitani et al.; and 3,680,496 to Westlake. U.S. Pat. No. 5,441,808 to Anderson et. al. discloses a thermally stable hot-melt moisture-cure polyurethane adhesive composition, and the patent lists PVC, among several other substrates, for use on which the adhesive is said to be suitable. Other patents disclose the advantages of pretreating the surface of certain articles by flame treatment or corona discharge to enhance the receptiveness of an adhesive to the article surface. Examples of such pretreating can be found in U.S. Pat. Nos. 5,425,825 to George et al.; 5,114,510 to Wright; 4,871,406 to Griffith; and 4,714,650 to Saburo et al. Still other patents disclose various PVC formulations that improve the processability and performance of the formulation. Examples of PVC formulations can be found in U.S. Pat. Nos. 5,185,404 to Folsch et al.; 4,668,740 to Okano; and 3,833,686 to Grochowski. An example of a plastic extrusion process can be found in U.S. Pat. No. 5,585,054 to Evans. None of these patents, alone or in combination, teaches or suggests a pallet or crate, or method for making a pallet or crate, that meets the stringent requirements of today's marketplace and that contains the performance advantages of traditional wood pallets while eliminating the problems associated with prior art wood and plastic pallets.
It is an object of the present invention to produce PVC structural products that have significantly improved properties when used in plastic pallets and plastic crates, namely:
1) substantially improved structural rigidity;
2) substantially improved heat deflection temperature;
3) substantially reduced coefficient of thermal expansion and contraction;
4) significantly improved impact properties;
5) significantly lower raw material costs;
6) significantly improved economics associated with the continuous extrusion process; and
7) significantly improved fire retardancy.
In addition to the above objects, it is a further object of the present invention to produce PVC pallets and crates made of the aforementioned PVC structural products that have significantly improved characteristics over wood pallets and other plastic pallets, namely:
1) significantly improved durability;
2) significantly improved ease of manufacturing;
3) significantly improved ability to customize sizes;
4) unique property of repairability;
5) full recyclability;
6) unique property of rackability;
7) substantially lighter;
8) significantly improved economics associated with the ease of assembly of the PVC structural products;
9) significantly improved economics associated with the elimination of customized tooling costs;
10) longer useful life; and
11) significantly more compatible with the environment.